Direct laryngoscopy & orotracheal intubation — blade types, Cormack-Lehane grade, BURP, ETT selection and confirmation

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Target exams

Red flags

• Oesophageal intubation is rapidly fatal if unrecognised. Direct visualisation of the tube passing through the cords is the gold standard during placement, but the definitive confirmatory test is sustained waveform capnography over several breaths; auscultation, chest rise and tube misting are not confirmation. Every intubation must be confirmed with capnography.
• The laryngoscope blade is lifted along the axis of the handle at roughly 45 degrees, never levered or pried against the upper incisors. Levering fractures teeth and fails to expose the glottis; the force is a lift, not a rotation.
• Cormack-Lehane grade three or four (epiglottis only, or epiglottis not visible) is the operational definition of the difficult direct laryngoscopy. Encountered unanticipated, it demands a change of plan, not a repeated failing attempt: optimise position, apply BURP, and move to a video laryngoscope or a supraglottic rescue.
• Endobronchial intubation (the tube advanced too deep) enters the right main bronchus and causes unilateral ventilation, barotrauma and contralateral collapse. Depth is set at three times the internal diameter at the lips (about 23 cm in men, 21 cm in women) and checked by bilateral air entry.
• The physiological difficult airway is dangerous independently of the anatomy. Hypoxaemia, hypotension and shock shorten the safe apnoea period and remove the cardiovascular reserve; the patient who is anatomically easy can be physiologically impossible, and resuscitation must accompany the intubation.